Effect of Lithium Salt on Lithium-Mediated Ammonia Synthesis

Abstract

Recently, the lithium-mediated nitrogen reduction reaction (Li-NRR) has emerged as a promising approach for electrochemical ammonia synthesis, facilitating more localized production. However, the systematic investigation of lithium salts in this process, especially when coupled with a hydrogen oxidation reaction (HOR) at the anode side in a continuous-flow reactor, remains largely underexplored. This study systematically investigates the effects of various lithium salts on Li-NRR selectivity and efficiency in a continuous-flow reactor coupled with the HOR at the anode. Among the evaluated salts, lithium tetrafluoroborate (LiBF4) demonstrated the highest NH3 selectivity of 61% under ambient conditions. Conversely, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) showed a significantly lower Faradaic efficiency (FE) of 18%, due to its decomposition and subsequent sulfur poisoning of the HOR catalysts. These findings highlight the importance of selecting appropriate lithium salts and establishing critical design principles for more efficient and stable electrolytes for Li-NRR and advancing sustainable ammonia synthesis.